A 3G mobile communication system aims to provide users to access a broadband wireless multi-media service at any time and any place. Currently, a Universal Mobile Telecommunications System (UMTS) has been developed. The UMTS provides a high-quality voice service, a high-speed access band, multiple service quality mechanisms, a real-time or non-real time voice/data service and a security mechanism. The UMTS further provides a multi-access service function (which currently provides phone call service and network service) and a video call function.
In general, a network configuration of the UMTS has three main parts, namely, a user equipment (UE), a UMTS terrestrial radio access network (UTRAN) and a core network (CN).
The user equipment is a mobile user terminal equipment, such as a 3G mobile phone, through which the user accesses the internet and makes phone calls.
The UTRAN provides the user equipment to access to the core network service, and includes a radio network subsystem (RNS). The RNS includes a radio network controller (RNC) and several nodes B. Each node B (or referred to as a base station) is in charge of radio transmission and radio reception for one or several mobile phones. The RNC controls radio resources.
The core network is in charge of signaling switch and interfaces with external networks, such as a public switched telephone network (PSTN), an integrated service digital network (ISDN) and the Internet.
The base station includes a home node B (HNB), which provides 3G wireless coverage to 3G mobile phones inside the households. The base station is connected to an existing home broadband service.
Along with the continuous advance in the 3G network, the Internet information services put more and more network loading on telecommunication operators, and may even affect the voice communication quality. If the Internet information services can be directly connected to an external network through the base station without going through the core network, the network loading for the telecommunication operators will be largely reduced.